On Wed, Nov 30, 2011 at 02:26:57PM -0800, Nicholas A. Bellinger wrote:
> If pSCSI's usage of blk_execute_rq_nowait() will enforce
> scsi_device->can_queue for us in order to prevent backend queue
> overflow, then it can be removed.
>
> All of the old scsi_execute_req() usage always needed this, so I was
> trying to be safe here.
Both enforce the can_queue limit, and as far as I know always have.
> Adding more context.
Let's remove the part just restatation the obvious facts from the code
first..
> > > + if (dev->enforce_dev_tcq) {
> > > + if (!dev->depth_left) {
> > > + spin_unlock_irq(&dev->execute_task_lock);
> > > + return transport_tcq_window_closed(dev);
> > > + }
> > > + dev->dev_tcq_window_closed = 0;
> > > + }
> >
> > Also note that the current transport_tcq_window_closed code is
> > really dumb. There is absolutely no need for the sleep, instead
> > the code incrementing depth_left should do a wakeup on
> > dev->dev_queue_obj.thread_wq.
>
> It already does do a wakeup on thread_wq after the sleep.
Which as I said is dumb. The wakeup needs to be happen from the thread
incrementing depth_left, that is freeing the ressource - a busywait
in the submission path does not help at all.
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